I have applied for a number of patents on dispensers for a gaseous, gas borne or droplet substance. In particular, in my prior International Patent Application, PCT/GB98/00770, at least as amended on entry in the European Regional Phase, there is described and claimed:
A dispenser for a gaseous, gas borne or droplet substance, the dispenser including:                a body having a mouthpiece with an inhalation/insufflation orifice at its end;        a junction in the body for a source of gas or evaporable liquid comprising or containing the said substance (the source being carried by the body); and        a breath actuatable valve, for controlling the release of said gas or liquid, comprising:        a valve inlet connected to the junction;        a valve outlet;        a flexible tube extending from the junction, between the inlet and the outlet, for receiving the said gas or liquid, the tube having a portion which is movable between a closed position in which the tube is kinked for closure of the valve and an open position in which the tube is un-kinked for opening of the valve; and        a movable member, for moving the movable portion of the tube to control its kinking, and being movably mounted in the body for movement by the act of inhalation from a rest position towards the orifice—or at least in the direction of air flow through the dispenser;        the tube being kinked to an obturating extent when the movable member is in a rest position and un-kinked when the movable member is moved on inhalation for release of the gas or liquid.        
Such a dispenser can loosely be classed as a breath actuated, kink valve dispenser and is referred to herein as “My Earlier Breath Actuated, Kink Valve Dispenser”.
With such a dispenser, in common with others of my design and other designs, there is advantage to the user in knowing how many doses are left in the reservoir of the substance source, the reservoir typically being an aerosol valve can, the can being an aluminium pressing.
Two approaches to dose measurement are known.
Firstly, dispensers actuated by depression of the end of the can towards the body of the dispenser body can be provided with electronic or mechanical counters which sense the number of depressions and count down to indicate exhaustion of the dispenser. This approach is costly.
A second approach is to provide the source with a transparent reservoir, typically of glass. Existing glass reservoirs have replicated the shape of the prior pressed aluminium can. Their shape renders difficult estimation of the number of doses remaining.